javascript中this用法实例详解

var point = {
 x : 0,
 y : 0,
 moveTo : function(x, y) {
   this.x = this.x + x;
   this.y = this.y + y;
   }
};
point.moveTo(1, 1)//this 绑定到当前对象，即 point 对象

var a = {
  aa : 0,
  bb : 0,
  fun : function(x,y){
    this.aa = this.aa + x;
    this.bb = this.bb + y;
  }
};
var aa = 1;
var b = {
  aa:0,
  bb:0,
  fun : function(){return this.aa;}
}
a.fun(3,2);
document.write(a.aa);//3，this指向对象本身
document.write(b.fun());//0,this指向对象本身
(function(aa){//注意传入的是函数，而不是函数执行的结果
  var c = aa();
  document.write(c);//1 , 由于fun在该处执行，导致this不再指向对象本身，而是这里的window
})(b.fun);

var x = 1;
function test(){
  this.x = 0;
}
test();
alert(x); //0

var point = {
 x : 0,
 y : 0,
 moveTo : function(x, y) {
   // 内部函数
   var moveX = function(x) {
   this.x = x;//this 绑定到了全局
  };
  // 内部函数
  var moveY = function(y) {
  this.y = y;//this 绑定到了全局
  };
  moveX(x);
  moveY(y);
  }
};
point.moveTo(1, 1);
point.x; //==>0
point.y; //==>0
x; //==>1
y; //==>1

var point = {
 x : 0,
 y : 0,
 moveTo : function(x, y) {
   var that = this;
   // 内部函数
   var moveX = function(x) {
   that.x = x;
   };
   // 内部函数
   var moveY = function(y) {
   that.y = y;
   }
   moveX(x);
   moveY(y);
   }
};
point.moveTo(1, 1);
point.x; //==>1
point.y; //==>1

var x = 2;
function test(){
  this.x = 1;
}
var o = new test();
alert(x); //2

var name = "window";
var someone = {
  name: "Bob",
  showName: function(){
    alert(this.name);
  }
};
var other = {
  name: "Tom"
};
someone.showName();   //Bob
someone.showName.apply();  //window
someone.showName.apply(other);  //Tom

var o = {
  x : 1,
  func : function() { console.log(this.x) },
  test : function() {
    setTimeout(function() {
      this.func();
    }, 100);
  }
};
o.test(); // TypeError : this.func is not a function

var o = {
  x : 1,
  func : function() { console.log(this.x) },
  test : function() {
    var _this = this;
    setTimeout(function() {
      _this.func();
    }, 100);
  }
};
o.test();

var o = {
  x : 1,
  func : function() { console.log(this.x) },
  test : function() {
    setTimeout(() => { this.func() }, 100);
  }
};
o.test();

var x = 1,
  o = {
    x : 10,
    test : () => this.x
  };
o.test(); // 1
o.test.call(o); // 依然是1